As the abovesaid type of indentation hardness meter, there has heretofore been proposed such an arrangement in which a quadrangular pyramidal impression made in a specimen is imaged by scanning through the use of a scanning image sensing device, first and second diagonal-length signals representing the lengths of first and second diagonals of the impression are obtained from the image output and a hardness signal representing the hardness of the specimen is derived from the first and second diagonal-length signals.
The conventional indentation hardness meter of such an arrangement possesses, however, defects that a complex, bulky and expensive scanning image sensing device is needed which is capable of imaging the impression by scanning its entire area two-dimesionally, that the arrangement for obtaining the first and second diagonal-length signals from the image output of the scanning image sensing device is extremely complex and that a relatively long period of time is required for obtaining the first and second diagonal-length signals.